The present invention relates to a procedure as defined in the claims and to an apparatus as defined in the claims for microbiological treatment of waste containing harmful substances.
In prior art, a procedure for the treatment of hazardous waste, especially oil-containing hazardous waste is known. In the procedure, to make hazardous waste harmless to the environment, the waste is stacked on the ground and treated with bacteria that use it for nutrition. A problem with this procedure is that it is difficult to maintain conditions and properties in the hazardous waste, e.g. temperature, humidity and pH value, that are optimal for bacterial activity. Another problem is that hazardous waste contains substances harmful to the environment, e.g. heavy metals, which remain unchanged regardless of bacterial activity and drift into the soil surrounding the stack.
In the context of the present invention, hazardous waste refers to waste that contains substances or compounds harmful e.g. to people, animals and/or the environment and that are to be prevented from getting into the soil, air or water systems, especially earth material, such as sand, clay, humus or the like, containing oil or its distillate fractions.
The object of the present invention is to eliminate the drawbacks described above.
A specific object of the present invention is to disclose a procedure that makes it possible to adjust and maintain optimal conditions for bacterial activity in hazardous waste and thus to achieve controlled improvement in the treatment of hazardous waste.
A further object of the invention is to disclose an apparatus for implementing the procedure, which can be used to prevent undecomposable environmental poisons from getting into the soil, atmosphere and water systems.
The invention is based on microbiological treatment of waste containing harmful substances. The waste is loaded into a waste treatment reactor, organic matter is added to the waste and the properties and conditions of the waste material are adjusted so as to make them favourable for bacterial activity. According to the invention, the waste is treated in the reactor substantially without agitation, and a substantially sufficient amount of oxygen, moisture and/or nutrients is supplied into the waste material.
In an embodiment of the procedure, oxygen, moisture, nutrients, organic matter and/or steam is/are added into the waste material during treatment to adjust the conditions.
According to an embodiment, nitrogen and/or moisture is added into the waste material substantially in conjunction with loading. Nitrogen can be added in the form of any kind of solution, e.g. 5% nitrogen solution. The amount of nitrogen solution may be e.g. 1-100 kg/25 m3 of waste material.
In an embodiment, oxygen, moisture, nutrients and/or steam is/are added via a pipe system placed at at least one level in the reactor substantially between the waste material. The pipe system may be of a disposable nature to facilitate the unloading of the waste from the reactor.
In an embodiment, organic matter is loaded in the reactor in layers, alternately with waste. The amount of organic matter loaded into the reactor may be e.g. 3-50% of the total mass of the material. The organic matter may consist of e.g. peat, shavings, wood chips, bark, straw and/or other lignocellulose based or other organic matter. A preferred kind of organic matter is bark chips.
According to an embodiment, heavy metals are washed off from the waste material and recovered. In an embodiment of the invention, the liquid used in the waste treatment process can be recirculated.
In an embodiment, aerobic and anaerobic alternation is employed. Alternation of oxidation-reduction areas can also be used in the procedure.
The invention allows hazardous waste, especially oil-containing hazardous waste, to be made harmless to the environment by treating it in a closed space in conditions optimal for the activity of bacteria that use the hazardous waste for nutrition. The treatment is fast and the dangerous substances contained in the hazardous waste can be easily reclaimed e.g. together with water/liquid/gas separated from the waste. From gases to be discharged into the atmosphere, harmful substances, such as VOC compounds (Volatile Organic Compounds), can be recovered by using a special filter before discharge of the gases into the atmosphere. From contaminated liquid/water, e.g. heavy metals can be recovered.
A further advantage of the procedure of the invention is waste treatment without agitation, which makes composting considerably easier.
A further advantage of the apparatus of the invention is that it can be transported to the place of treatment of thee waste, e.g. contaminated soil, which means that the treatment involves no waste transport expenses. Another advantage of the apparatus is that it is applicable in cold conditions, e.g. due to thermal insulation and steam supply.
In addition, the procedure and apparatus provide the advantage of simple and cheap composting and energy-saving operation.